Microorganisms are causative or contributory agents in the etiology of dental caries, gingivitis and related periodontal disease(s). The pathogenicity of Gram-positive streptococci and Gram-negative Fusobacteria resides in part in the capacity of these species to form a variety of organic acids and toxic sulfur-containing derivatives as end products of carbohydrate and amino acid fermentation. Elucidation of the biochemical steps and the genetic basis for regulation of these energy-yielding pathways provides the rationale for this research program. Significant accomplishments of the past year include: 1) Demonstration that the triosephosphate gene (tpi) of Lactococcus lactis is monocistronic; 2) Elucidation of the role(s) of lysine 214 and cysteine residues in activity and cytotoxicity of beta-cystathionase from Bordetella avium; 3) Purification, cloning, sequence analysis and expression of maltose 6-phosphate:6-phosphohydrolase from Fusobacterium mortiferum ATCC 25557; 4) Cloning and site-directed mutagenesis of catalytically functional residues of Tn5306-encoded N(5)-(carboxyethyl) ornithine synthase from L. lactis; 5) Purification of a novel cellobiose 6-phosphate:6-phosphohydrolase from F. mortiferum; 6) Chemical synthesis of unique methylumbelliferyl analogs of phospho-alpha and phospho-beta-glucosides for use as fluorogenic reporter molecules for study of the regulation of gene expression in Fusobacteria. Results from this research program have been published in four papers in peer-reviewed, international journals.